Method of treating rubber compounds



Patented Sept. 15, 1931 PAUL A. DAVIS, or AKRON, OHIO, assrenon o Tim GoonYnAR name's Rosina COMPANY, or AKRON, OHIO, A, ooao'iurron or onto METHOD or .TREAT'LI'ING Etienne ooiltrounns No Drawing.

This invention relates to methods of treating the surfaces of unvulcanized rubber and method of treating surfaces of unvulcanized rubber whereby to render them non-adhesive at normal temperatures.

Another object of the invention is to provide a method of treating rubber surfaces which results in an increase of the adhesive nature of the rubber at high temperaturest I the same manner as the zinc compounds here 65 and more perfect unions between rubber surfaces or between rubber and fabricsurfaces.

An additional object of the invention is to provide a method of treatingrubber surfaces to obtain the above described results, which; involves the use of a non-toxic, readily fusible dusting powder.

Unoured rubber, when subjected to the milling requisite to incorporation of the sulphur, pigments and other compounding in gredients employed in the vulcanization:- thereof, becomes relatively plastic and tacky in nature, and because of this property it tends to adhere to any object with which it comes in contact. In order to overcome this difliculty, it has heretofore been customary to dust the surfaces of the compounded mate rial with a fine powdery material, such as talc, soapstone or potato starch to form a non-adhesive film thereon. These substances 1 effectively prevented the adhesion of the un-- cured rubber to other bodies with which theycame into contact. However, when the rub-; her was incorporated into articles and vulcanized, the powder being of relativelyinfusible nature, tended to create lines of cleavage between two contacting surfaces.

In order to obviate this difliculty, it has been proposed to substitute zinc stearate for the usual powdery substances. This compound has a point of fusionbelow that temperature which is ordinarily employed in,

ztheyh-ave been found particularly desirable vulcanizing rubber, and as a result the compound fuses during the process of curing the rubber and then flows and blends with the latter, thereby permitting the formation of a treated surfaces.

-, thereaetio'in product in order to particles thereof from coalescing.

Application filed April s, 1929.} serial no. 353,679.

perfect unionbetween the various surfaces. This; invention consists in the discovery that soaps of metals having atomic weights of. from 24 to 27, such as magnesium and aluminum, may be substituted for the zinc stearate heretofore employed as a dusting .powder for unvulcanized rubber. These soaps efiectively prevent adhesion at normal temperatures. However, when the uncured rubber so coated or'dusted is incorporated into rubberartioles and is exposed to the heat of vulcanization; theyreadily fuse at com v-paratively low temperatures and then flow and blend with the rubber inz -substantially tofore-proposed. The soaps, when so blended, do not impair adhesion between the Infact, in some cases it appears that adhesion is actually improved. This property is probably due to the fact thatvthe compounds when .fused'act to some extent as plasticizers which enhance the tackyor adhesive properties of the rubber.

The oleates, stearates and palmitates of magnesiumand aluminum are specific exam- 7 ples of compoundswhich may be employed in 1 practicing the invention.-

Substantially any convenient method may be employed in the preparation of the magnesium? or aluminumsoaps, although it has 30 been found by practice to be convenient to reduce thefatty acid or .fat to a soluble sodium soap'and then to treat the soap with a soluble salt pf aluminum or magnesium.

Care should bev taken to'emp'loy only tlie0-" s5 rfetical .qu'antitiesbf the various ingredients. Thefinal product should be filtered and dried at a temperature well below that of fusion of prevent the The compounds may be employed for dusting substantially any surfaces which it; may be desirable to render non-adhesive. while they'are an uncured state, but which it is desirdshouldadhere to otherSurf-aces dur ingthe process of-Vulcahi-zing; For example,

for dusting the rubber tubing which is employed as a liner for ordinary hose. This ma l bysubjecting the hose to vulcanization they readily fuse with the main body of the rubber. e

incorporation into the body of a hose, and because of the adhesive nature of the uncured compound the folds thereof if untreated tend. to adhere to each other. Ordinarily, dusting powders cannot be employed on the surfaceof such, tubing because they donot blend withthe rubber during. the course-of 1 vulcanization to permit the surface of the tubing to unite with the inner surface of the braid which is employed towrap thetubing'.

When the new dusting powders are'Substi tuted for the powders heretofore used these difliculties are entirely obviated, asthenew materials prevent adhesion between the tacky surfaces at ordinary temperatures, but

Furthermore, the compounds are non-toxic 1n character. Hence their use does not necessitate the employment of special ventithem.

*lator systems and other precautions to prevent poisoningof the workmen that handle 1 have described only the pre- Although ferred embodiment of theinvention, it will I comprises dusting the tion which comprises dusting the surfaces with a soap of magnesium.

8. A method of treating rubber which comprises dusting the surface thereof with a soap of a metal selected from a group consisting ofmagnesium and aluminum, bringing the dusted surface. into contact with the surface of another body, whole to vulcanization. 91A methodof treating rubber which surface thereof with a soap of magnesium, bringing the dusted 'surfaceinto contact with the surface of another body, and subjecting the whole tovulcanization.

In witness whereof, I have hereunto'signed my name. c Y 1 Si ned at Akron, in the county of Summit and tate of Ohio, U. S. A., this .6th day of April, 1929.

7 PAUL A. DAVIS.

and subjecting the be apparent to those skilled in the art that V it is not so limited, but that various modifications maybe madetherein without departing from the spirit of the invention or-from the scope of the appended claims.

WhatIcla'im'isr V LA methodof-treating the surfaces of uncured rubber which comprises dusting them with a powder comprising a soap of a metal having an atomic weight between 24 and-27.

-2. A method treatingthe of ,7 uncured rubber in order to reduce the tacky character thereof which comprises dusting them with a soap of a metal selected from a 1 L-m'inum.

group consisting of magnesium "and alu- -3.A- method oftreatingthe surfaces of i i v uncured rubber in order to reduce the tacky -character thereof at ordinary temperatures which'comprisesdusting the surfaces with a soap of magnesium.

i 4. A 7 method of reducing the adhesive character -of unvulca-nized rubber at ordinarytemperatures which comprises dusting i the surface thereof with a stearate of magnesium.

tween surfaces of rubberduring vulcaniza-' tion, which c'omprises dusting the surfaces with a soap of a metal havinga weight of 24 to 27. a. 6. A method tween surfaces of rubber during vTu1caniza- 5. A methodof promoting the union bea I of promoting the union be-- .1

tion which comprises dusting the surfaces p with a soap of-a metal selected from agroup c consisting of magnesium and aluminum.

' 7 L A method ofpromoting'the union be- I tween surfaces 4 of rubber during vulcaniza- 

